Matrix injector driver circuit

ABSTRACT

A fuel injector control circuit reduces the number of gates required by arranging high side and low side gates in a matrix. Each coil is selectively activated by activating a unique pair of a high side gate and a low side gate, thus reducing the total number of gates required.

RELATED APPLICATIONS

[0001] This application is a divisional of U.S. Ser. No. 09/703,537;filed on Nov. 1, 2000, which claims priority to U.S. ProvisionalApplication No. 60/162,839, which was filed Nov. 1, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to fuel injector controlcircuits.

[0003] Known fuel injector control circuits generally comprise an opencoil and a close coil for each fuel injector. To inject fuel into thecylinder, it is necessary to activate the open coil and then the closecoil. Some applications require that the close coil on a given cylinderbe activated before the associated open coil is deactivated. This isknown as simultaneous excitation.

[0004] Known fuel injector fuel circuits connect each coil to the powersupply with a different switch (such as a FET or other gate). Thus, foran 8 cylinder engine, 16 high side gates were required, each withassociated drive circuitry.

[0005] When a coil is energized, some energy is stored in a magneticfield that surrounds the coil. When the coil is de-energized, it isdesirable to recover some of the energy that was stored in the magneticfield. This energy recovered is done by a known technique called“recirculation.”

SUMMARY OF THE INVENTION

[0006] The present invention provides cost saving by reducing the numberof high side gates and the associated drive circuitry from 16 to as fewas 4 (for an eight cylinder engine). Various configurations areillustrated herein, with different benefits and features in each.However, as a general principal, each of these utilizes high and lowside gates which selectively activate selected coils via a matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Other advantages of the present invention will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

[0008]FIG. 1 is a high-level schematic of the fuel injector controlsystem of the present invention;

[0009]FIG. 2 is a schematic for a first circuit for controlling coilsaccording to the present invention;

[0010]FIG. 3 is a schematic of a second, alternate circuit forcontrolling coils according to the present invention;

[0011]FIG. 4 is a schematic for a third circuit for controlling coilsaccording to the present invention.

[0012]FIG. 5 is a schematic of a fourth alternate circuit forcontrolling coils and according to the present invention;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0013] A fuel injector control circuit 20 is shown schematically inFIG. 1. A microcontroller 22 is programmed generally to control highside drivers 24 to drive high side gates 26 and low side drivers 28 todrive low side gates 30. The high side gates 26 and low sides gates 30selectively activate coils 32, which in turn selectively activateinjectors 34.

[0014] Generally, the present invention reduces the number of high sidegates 26. This is accomplished by treating the coils as a matrix,wherein each coil is selected by selective activation of one of the highside gates and one of the low side gates.

[0015] For example, a first circuit 40 is shown generally in FIG. 2,including high side gates 26, including gates Q1, Q2, Q5, Q6, Q9, Q10,Q13, Q14. The circuit 40 further includes low side gates 30, includingQ17—Q20. This circuit 40 illustrates 16 coils OC_A—H and CC_A—H. In thecircuit 40, high side gate Q1 connects odd coil OC₁₃A and odd coil CC_Aselectively to power supply. In circuit 40, each of the high sidedrivers connects the open coil and associated close coil for one of the8 injectors.

[0016] The low side gates 30, Q17-Q120 selectively connect differentgroups of the coils to ground. For example, as can be seen in FIG. 2,Q17 selectively connects the odd open coils, Q18 selectively connectsthe odd close coils, Q19 selectively connects the even open coils andQ20 selectively connects the even close coils. Thus, any one of the 16coils can be selectively individually activated by switching on theproper pair of a high side gate 26 and a low side gate 30. The diodesD1-D16 are placed in series with each coil and prevent interactionbetween the coils. The operation of the first circuit 40 is furtherdemonstrated in the following table. TABLE 1 Q17 Low Q18 Low Q19 Low Q20Low side driver side driver side driver side driver for odd for odd foreven for even open coils close coils open coils open coils Q1 High sideOC_A CC_A driver for cyl. A Q2 High side OC_B CC_B driver for cyl. B Q5High side OC_C CC_C driver for cyl. D Q6 High side OC_D CC_D driver forcyl. D. Q9 High side OC_E CC_E driver for cyl. E Q10 High side OC_F CC_Fdriver for cyl. F Q13 High side OC_G CC_G driver for cyl. G Q14 Highside OC_H CC_H driver for cyl. H

[0017] In this example, because gates are connected on common points onthe high side of open and close coils in the same cylinder, simultaneousexcitation cannot be performed. On the other hand, the advantages ofthis configuration include that the failure of one high side gate willonly disable one cylinder and that three wire coils (with the high sideconnection with both open and close coils on the same wire) can be used.

[0018] A preferred method and apparatus for controlling of low sidegates 30 is disclosed in co-pending patent application U.S. Ser. No.09/703,537 entitled “CONTROL OF DRIVER CURRENT VIA LOW SIDE GATES” filedon Nov. 1, 2000, the assignee and inventors of which are the same as theassignee and inventors of this patent application, and which is herebyincorporated by reference fully as if repeated herein.

[0019]FIG. 3 illustrates a second circuit for activating the coils. Ascan be seen, the second circuit 50 requires only 4 high side gates. Inthe circuit 50, each of the high side gates, Q1, Q5, Q9 and Q13 operatesthe open and close coils for two cylinders. Low side gates 30, Q17-Q20,operate identically as in FIG. 2. Thus in this circuit 50, any of thecoils can be selectively activated by switching the appropriate pair ofhigh and low side gates. This is shown in the Table 2 below. TABLE 2 Q17Low Q18 Low Q19 Low Q20 Low side driver side driver side driver sidedriver for odd for odd for even for even open coils close coils opencoils open coils Q1 High side OC_A CC_A OC_B CC_B driver for cyl. A andB Q5 High side OC_C CC_C OC_D CC_D driver for cyl. C and D Q9 High sideOC_E CC_E OC_F CC_F driver for cyl. B and F Q13 High side OC_G CC_G OC_HCC_H driver for cyl. G and H

[0020] Some advantages of this configuration are that the failure of onehigh side FET will only disable two cylinders, this configuration onlyutilizes four high side gates and that this version allows the use ofthree wire coils. The disadvantage of this configuration is thatsimultaneous excitation of the open and close coils on the same cylinderis not possible.

[0021]FIG. 4 illustrates a third circuit 60 for operating the fuelinjector coils for operating. In this third circuit 60, 8 high sidegates Q1, Q2, Q5, Q6, Q9, Q10, Q14 are no longer connected to two coilsin the same cylinder (as in FIG. 3). Rather, each high side gate Q1, Q5,Q9, Q13 is connected to a pair of open coils (one even, one odd), whilethe gates Q2, Q6, Q10 and Q14 are connected to a pair of close coils(one even, one odd). The low side gates 30 operate as described abovewith respect to FIG. 1 in this third circuit 60. Because the open andclose coils on any cylinder do not share any high side driver,simultaneously excitation can be utilized. The operation of this circuit60 is further described in the Table 3, below. TABLE 3 Q17 Low Q18 LowQ19 Low Q20 Low side driver side driver side driver side driver for oddfor odd for even for even open coils close coils open coils open coilsQ1 High side OC_A OC_B driver for cyl. A and B open coils Q2 High sideCC_A CC_B driver for cyl. A and B close coils Q5 High side OC_C OC_Ddriver for cyl. C and D open coils Q6 High side CC_C CC_D driver forcyl. C and D close Q9 High side OC_E OC_F driver for cyl. E and F opencoils Q10 High side CC_E CC_F driver for cyl. E and F close coils Q13High side OC_G OC_H driver for cyl. G and H open coils Q14 High sideCC_G CC_H driver for cyl. G and H close

[0022]FIG. 5 illustrates a fourth schematic 70 including 4 high sidegates, Q1, Q5, Q9 and Q13. High side gate Q1 selectively connects opencoils A, B, C, D to power supply, while Q5 selectively connects closecoils A, B, C, D. Similarly, gate Q9 selectively connects open coils E,F, G, H to the power supply while gate Q13 selectively connects closecoils E, F, G, H to the power supply. In schematic 70, the low sidegates 30 are configured differently, as shown. Gate Q17 selectivelyconnects open coils 1 and 5 and close coils 2 and 6 to ground. Theoperation of the remaining gates and activation of the remaining coilsare illustrated in the following table as well as in schematic FIG. 5.TABLE 4 High Side Driver High Side Driver High Side Driver High SideDriver Q1 Q5 Q9 Q13 1-4 Open Coils 1-4 Close Coils 5-8 Open Coils 5-8Close Coils Low Side Driver Open Coil #1 Close Coil #2 Open Coil #5Close Coil #6 Q17 1 and 5 Open 2 and 6 Close Low Side Driver Open Coil#2 Close Coil #1 Open Coil #6 Close Coil #5 Q18 2 and 6 Open 1 and 5Close Low Side Driver Open Coil #3 Close Coil #4 Open Coil #7 Close Coil#8 Q19 3 and 7 Open 4 and 8 Close Low Side Driver Open Coil #4 CloseCoil #3 Open Coil #8 Close Coil #7 Q20 4 and 8 Open 3 and 7 Close

[0023] The circuit 70 enables both recirculation and overlap by a morecreative arrangement of the low side drivers. On any given cylinder theopen coil and close coil do not share either a high side driver or a lowside driver.

[0024] As shown above, the present invention reduces the number of gatesand associated driver circuitry required, thus reducing cost. Someembodiments described still permit simultaneous excitation andrecirculation. Of course, although a few arrangements have beendescribed, additional different arrangements utilizing the inventiveconcepts described herein could also be utilized.

[0025] In accordance with the provisions of the patent statutes andjurisprudence, exemplary configurations described above are consideredto represent a preferred embodiment of the invention. However, it shouldbe noted that the invention can be practiced otherwise than asspecifically illustrated and described without departing from its spiritor scope.

what is claimed is:
 1. A fuel injector control circuit comprising: aplurality of coils, including a plurality of open coils and a pluralityof close coils; a plurality of first gates each selectively connectingmore than one of said plurality of open coils and more than one of saidplurality of close coils to a power supply; and a plurality of secondgates selectively connecting said plurality of coils to ground.
 2. Thecircuit of claim 1 wherein each of said plurality of second gatesselectively connects more than one of said plurality of said coils toground.
 3. The circuit of claim 2 wherein each of said plurality ofsecond gates selectively connects more than one of said plurality ofopen coils to ground or more than one of said plurality of close coilsto ground.
 4. The circuit of claim 1 each of said plurality of secondgates selectively connects at least four of said coils to ground.
 5. Thecircuit of claim 4 wherein at least one of said plurality of secondgates selectively connects at least four of said open coils to ground.6. The circuit of claim 5 wherein at least one of said plurality ofsecond gates selectively connects at least four of said close coils toground.
 7. A fuel injector control circuit comprising: a plurality ofcoils including a plurality of open coils and a plurality of closecoils; a plurality of high side gates each selectively connecting morethan one open coil and more than one close coil to a power supply; aplurality of low side gates, each selectively connecting at least two ofsaid plurality of coils to ground, including a first low side gateselectively connecting at least two of said close coils to ground, and asecond low side gate selectively connecting at least two of said opencoils to ground.
 8. The circuit of claim 7 wherein each said low sidegate selectively connects at least four coils to ground.
 9. The circuitof claim 8 wherein a first half of said low side gates selectivelyconnects at least four open coils to ground.
 10. The circuit of claim 9wherein a second half of said low side gates selectively connects atleast four close coils to ground.
 11. The circuit of claim 7 whereinsaid plurality of high side gates is equal in number to said pluralityof low side gates.
 12. The circuit of claim 11 wherein each of saidplurality of low side gates selectively connects one fourth of theplurality of coils to ground.
 13. A method for controlling a pluralityof fuel injectors including the steps of: a) associating each of aplurality of pairs of coils with each of a plurality of fuel injectors,each said pair comprising an open coil and a close coil; b) selectivelyconnecting two of the pair of coils to a power source with one of aplurality of high side gates; c) selectively connecting at least two ofsaid open coils to ground with a first low side gate; d) selectivelyconnecting at least two of said close coils to ground with a second lowside gate; and e) activating each of said coils based upon activation ofa unique pair of one of said high side gates and one of said low sidegates.